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ELECTROLYSIS
The chemical changes produced in a solution containing ions when electricity is passed through it is known as the process of electrolysis.

Electrolysis takes place in an electrolytic cell. Electrolytic cells are the types of cells constituting an anode, a cathode, and an electrolyte where the two electrodes are connected externally using a battery. Anode is a positively charged electrode of any metal. Cathode is a negatively charged electrode of any other (or the same) metal. Electrolyte is a solution containing ions, which are the carriers of electricity.

Let us look into the mechanism of electrolysis by considering an example. Consider an electrolytic cell consisting of two platinum electrodes connected externally and with aqueous NaCl solution as electrolyte. The aqueous NaCl solution contains Na+, Cl-, H+ and OH- ions. When electricity is passed, positively charged ions move to cathode and negatively charged ions move towards anode. That is the Na+ and H+ ions show tendency to move towards cathode and Cl- and OH- show tendency to move towards anode.

Each ion has its own velocity, among which H+ ions have the highest. Thus moves faster than the other ions to reach the cathode. During this movement, Na+ ions are left behind. After H+ ions, Cl- ions have the next highest velocity. This allows the Cl- ions to move faster and reach the anode, while the OH- ions are left behind. Thus, chlorine gets deposited at the anode and gives away two electrons. These electrons move through the external circuit to the cathode, which is accepted by the hydrogen ions reaching the cathode. This causes the liberation of hydrogen gas at the cathode and chlorine gas at the anode. The ions which are left in the solution, Na+ and OH- combine to form NaOH. Thus we obtain an electrolyte rich with NaOH at the end of electrolysis.

The cell reactions are as follows: At anode, 2Cl ---> Cl2 + 2e- At cathode, 2H+ + 2e ---> H2

Since these ions are charged, their flow creates current. Flow of ions from anode to cathode causes flow of current from cathode to anode.